In...the...60s-70s maybe. Today's V8 mustangs and camaros pump out 400-700HP depending on model. Yea fuel mileage still sucks but it's improved from those old models. Definitely not something you should get if you want fuel efficiency.
The 6.2L LT1 in the Camaro SS I owned got about 16-18 mpg city and 27-30mpg highway. Its actually comparable to the 2.5T SUV I drive now with the city mileage being a bit better in the SUV and the highway mileage worse than the Camaro.
The Rover V8 began life as the Buick 215, an all-aluminium OHV pushrod engine introduced in 1960 for the 1961 US model year (it was on their drawing boards in the late 1950s).
The 3.0 3VZFE from Toyota was always mocked as the “fuel efficiency of a V8, power of a 4 cyl”. The motor was a joke and the 5VZFE that came later was much improved.
Ford does decent with their V8 cars (they’ve had most issues with the 1.0, 1.5, and 2.7 ecoboosts), although the EPA ratings are tight. To get a good idea you’d have to compare equally, like finding another 5.0L, 480hp car that weighs 4,000 lbs (or at least that ballpark). they’re not terribly common.
I think the most common failure on a mod family V8 was either cam phasers or spark plugs. Which thankfully they fixed on the coyote. Other than that the car will die before the engine.
When I bought my 2016 mustang, I got 27.5 mpg on the trip home. I’ve averaged 30 before. They’re efficient if you stay under 3k rpm’s most of the time. City driving they’re ok, I get 18. Averaged over the life of the car I have got 24 mpg total. Which for a 3,800lb 435hp car is pretty damn good.
Throwing that Americans get bad mpg out of V8’s is a bit skewed. Gas is cheap here (relatively) and they’re mostly in trucks/suv’s and not cars. Like currently it’s $2.50/gallon at my Costco.
Not to mention, heavy duty “light trucks” like the F250 or GM2500 and up, do not have to adhere to any mileage standards and are exempt.
I got my first one a couple years ago. It's so nice having the torque and being able to do 100mph at 2500rpm through the middle of no where.
I am so tired of buying gas. I average 26 so not terrible but it's premium and I commute 70 miles a day. My next car will most likely be a hybrid. I can't justify the waste of money and resources just to have a bit of fun.